1. Field of the Invention
The invention pertains to paint circulation systems wherein makeup paint is supplied through an injection pump operated by a "smart" motor and a bypass permits a constant monitoring of the paint viscosity, volume of paint pumped, and circulating motor wear, while minimizing paint settling and degradation.
2. DESCRIPTION OF THE RELATED ART
In manufacturing operations, it is often necessary to utilize sophisticated painting systems. In such painting systems, a variety of pumps and controls are utilized therewith to control the distribution and application of paint, such as shown in U.S. Pat. Nos. 4,030,857 and 4,238,073.
In large paint systems wherein a plurality of colors are available for instant use, each color requires a separate distribution system, and, conventionally, each system will include a circulation network wherein a circulation pump causes paint to flow through the network conduits. The network includes a plurality of paint distributors, such as spray guns or spray nozzles, which may be fixed, robotically operated or hand held, and one or more of the paint distributors may be in operation at a time. It is necessary to design the circulation system to be capable of handling sufficient paint if all of the distributors are simultaneously in operation, but usually, only a small percentage of the capacity of the circulation network is being used at any one time.
Paint circulation systems are basically "closed" wherein the paint circulates in a loop, and it is necessary to add paint to the loop to replace that ejected from the nozzles. The circlation of the paint is at a high rate and the paint will be cycled many times if usage is low. Problems have been experienced with existing paint circulation systems with respect to paint particles settling within the network conduits, and degradation of the paint occurs during extended circulation, including the degradation of metallic flakes and the like which may be added to the paint for aesthetic purposes. Additionally, existing paint circulation systems do not permit a ready indication of the volume of paint being used, nor indicate the viscosity of the paint. As viscosity changes the quality of the applied paint will change, and to provide optimum results a variety of paint characteristics need to be known which are not available with conventional paint circulation systems.
In the assignee's U.S. Pat. No. 4,653,532, a paint circulation system is shown having an injector pump. However, in this system the low pressure return line from the paint distributors is directly fed into the injector pump inlet, and as such, the injector pump is supplied from both the distributor return line and a paint supply reservoir.